If so, are there additional API calls that need to be made from the one's listed in addFundingSource in order to have both under a single Dwolla account?
At the moment I have no way of generating both account types so I can't provide code, but obviously it would help to know if this is even possible first.
As long as a bank account supports ACH transactions, it doesn't matter to Dwolla whether the bank account is intended for for-profit or non-profit use. You should be able to add both kinds of funding sources to a single Dwolla account.